The best look yet at mysterious brown dwarfs, strange cosmic oddities that blur the lines between stars and planets, has revealed just how large and cold they really are, scientists say. In fact, the weird "failed stars" only get as hot as your kitchen oven.

The new discovery may shed light on the formation and evolution of distant alien worlds, researchers added.

Starlike bodies known as brown dwarfs are often billed as failed stars because they are larger than planets, but too small to trigger nuclear fusion and ignite into the brilliance of a full-fledged star.

As such, brown dwarfs have only what little heat they are born with.

These new findings suggest the coldest brown dwarfs are between about 260 and 350 degrees Fahrenheit (125 and 175 degrees Celsius), with masses five to 20 times greater than the size of Jupiter. The temperature of the sun, for example, is about 10,000 F (5,500 C) at its surface.

"These objects we were studying were suspected to be colder than anything else that had previously been discovered in the solar neighborhood," said study lead author Trent Dupuy, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Several hundred have been detected to date.